Perhaps you should try some spelling variations:
"factores politicos" » "actos politicos", "valores politicos", "factores biologicos"
"factores bioticos" » "factores biologicos", "factores climaticos", "factores geneticos"
"factores clinicos" » "factores clinico", "factores climaticos", "factores tecnicos"
"factores criticos" » "factores critico", "factores critica", "factores critical"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("factores politicos") or ((("factores bioticos") or ("factores clinicos"))))) or ((("actores politicos") or ("factores criticos"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("factores politicos") OR ((("factores bioticos") OR ("factores clinicos"))))) OR ((("actores politicos") OR ("factores criticos")))).
• Removing quotes may allow a broader search: (((( factores politicos ) or ((( factores bioticos ) or ( factores clinicos ))))) or ((( actores politicos ) or ( factores criticos )))).
• Adding a wildcard symbol may retrieve word variants: (((("factores politicos") or ((("factores bioticos") or ("factores clinicos"))))) or ((("actores politicos") or ("factores criticos"))))*.